The assignee of the present invention manufactures and deploys spacecraft for, inter alia, communications and broadcast services. Market demands for such spacecraft have imposed increasingly stringent requirements on spacecraft payloads. Particularly, there are increasing demands for more bandwidth and a consequential need to exploit higher frequency bands. With the advent of HD TV and other high data rate applications, for example, an increased demand for Ka-band (30 GHz uplink, 20 GHz downlink) satellite payloads has been observed.
Satellite communications payloads are typically channelized using narrow band filters to facilitate reamplification. The increase in total bandwidth combined with increased requirements for spatial frequency reuse with “spot” beam antennas results in a need for larger quantities of filters, and a corresponding pressure to decrease filter size, weight, and cost, while still providing a high “Q factor” and excellent temperature stability.
At frequencies below Ka-band, such as, for example, C and Ku-bands, dielectric resonator (DR) filter technology is commonly used. Such filters are described, for example in U.S. Pat. No. 6,297,715, assigned to the assignee of the present invention, and hereby incorporated into the present application in its entirety. Modifying known DR filters to operate at higher frequencies, however, would conventionally require reducing the size of critical components, such as the DR itself, tuning components, and the like. Consequently, Ka-band filters of the prior art generally employ air-filled cavity filters rather than DR filters so as to avoid the need to integrate extremely small resonators and ancillary components and suffer the consequential penalty in manufacturing cost, reliability, and/or filter performance. As a result, conventional Ka-band filters are disadvantageously large and heavy. Referring now to FIG. 1, for example, a comparison is provided of the respective sizes of a Ku-band DR filter 101 and a Ka-band air filled cavity filter 102.